package L1;

import java.util.Scanner;

public class _050 {
    /**
     * 倒数第N个字符串
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int L=0;
        int N=0;
        L=sc.nextInt();
        N=sc.nextInt();
        int number = 1;
        for(int i=0;i<L;i++) {
            number = number*26;
        }
        int count = number-N;
        char ch[] = new char[L];
        int i=0;
        while(L-->0) {
            ch[i++] = (char)('a'+(count%26));
            count = count/26;
        }
        for(int j=i-1;j>=0;j--) {
            System.out.print(ch[j]);
        }
    }
}
